Spindle motor and storage disk drive

ABSTRACT

A motor includes a stationary portion and a rotating portion. The stationary portion includes a shaft portion and an upper thrust portion. The upper thrust portion includes a tubular first outer circumferential surface arranged radially outside the upper thrust portion, and a tubular second outer circumferential surface arranged above the first outer circumferential surface. The rotating portion includes a sleeve portion, a tubular portion, and an annular cover portion. The annular cover portion includes a plate portion and an inner annular projecting portion arranged to project upward or downward. An inner circumferential surface of the inner annular projecting portion is arranged above an inner circumferential surface of the tubular portion. An upper seal portion includes a surface of a lubricating oil located therein. The inner circumferential surface of the inner annular projecting portion and the second outer circumferential surface are arranged opposite to each other with an axially extending gap therebetween.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a spindle motor and more specificallyto a spindle motor for use in a storage disk drive.

2. Description of the Related Art

Motors including a bearing mechanism using fluid dynamic pressure haveoften been used in storage disk drives. A spindle motor disclosed inJP-A 2009-136143 includes a fixed shaft, an annular bearing component, arotor component, and an annular cover. The bearing component is arrangedon an upper end portion of the fixed shaft. The bearing component isintegrally provided with the fixed shaft. The rotor component isarranged radially outward of the fixed shaft. The annular cover isarranged above the bearing component. A radially outer end portion ofthe annular cover is adhered to an upper end portion of the rotorcomponent. An outer circumferential surface of the bearing component isarranged opposite an inner circumferential surface of the upper endportion of the rotor component. A seal gap is defined between the outercircumferential surface of the bearing component and the innercircumferential surface of the upper end portion of the rotor component.The seal gap is covered by the annular cover. Paragraph [0043] of JP-A2009-136143 states: “The annular cover 330 defines a labyrinth seal 348arranged to additionally seal the seal gap 332 together with an upperend surface of the bearing component 318.”

Another conventional dynamic pressure fluid bearing apparatus includedin a spindle motor is disclosed in JP-A 2007-162759. This conventionaldynamic pressure fluid bearing apparatus includes a shaft body and atubular sleeve body inside which the shaft body is inserted. The shaftbody is fixed to a base plate of the motor. The sleeve body is fixed toa rotor of the motor. The shaft body is provided with a first thrustflange and a second thrust flange. The first thrust flange and thesecond thrust flange are both annular and are arranged on an upper sideand a lower side of the sleeve body, respectively. In the dynamicpressure fluid bearing apparatus, a radial bearing portion is definedbetween the shaft body and the sleeve body, and a thrust bearing portionis defined between each of the two thrust flanges and the sleeve body.In addition, the sleeve body includes communicating holes definedtherein to provide communication between two thrust gaps. Tapered sealportions are defined in the vicinity of upper and lower end openings ofthe communicating holes.

Another example of a known fluid dynamic bearing motor is disclosed inU.S. Pat. No. 6,991,376. This fluid dynamic bearing motor includes ashaft, a top plate, a bottom plate, and a hub. The top plate is fixed toan upper end of the shaft and the bottom plate is fixed to a lower endof the shaft. The hub is arranged between the top plate and the bottomplate, and is supported so as to be rotatable with respect to the shaft.The hub includes a recirculation channel extending therethrough definedtherein. An upper portion of the hub includes a projecting portionarranged radially outward of an outer edge portion of the top plate. Acapillary seal is defined between the projecting portion and the outeredge portion of the top plate. A lower portion of the hub includesanother projecting portion arranged radially outward of an outer edgeportion of the bottom plate. A capillary seal is also defined betweenthe other projecting portion and the outer edge portion of the bottomplate. The influence of a pressure gradient of a lubricating oil in eachof the capillary seals is minimized by the recirculation channel beingarranged radially inward of the capillary seals.

In some motors, a cap member is arranged in a rotating portion to covera seal gap. The motor described in JP-A 2009-136143 is an example of oneof these motors. In such a motor, there is a gap between the cap memberand a component of a stationary portion which defines the seal gap, andthis gap may permit an evaporated lubricating oil to pass therethroughto an outside of the motor. Moreover, an attempt to ensure sufficientrigidity of the cap member by increasing the thickness of the cap memberleads to a failure to reduce the overall thickness of the motor.Moreover, a reduction in the thickness of the cap member may result in areduction in the precision with which the cap member is shaped, and maylead to a contact of the cap member with the stationary portion duringrotation of the motor.

In the motor disclosed in JP-A 2007-162759, a difference in pressurebetween the upper tapered seal portion and the lower tapered sealportion is large because of the large axial distance between a surfaceof a lubricating oil in the upper tapered seal portion and a surface ofthe lubricating oil in the lower tapered seal portion. Therefore, whenthe motor is oriented in a variety of directions, the surface of thelubricating oil in each tapered seal portion will fluctuate greatly.Because of this, it is necessary to provide a complicated design toprevent a leakage of the lubricating oil.

Similarly, with respect to the motor disclosed in U.S. Pat. No.6,991,376, a difference in pressure between the upper capillary seal andthe lower capillary seal is large because of the large axial distancebetween a surface of the lubricating oil in the upper capillary seal anda surface of the lubricating oil in the lower capillary seal.

SUMMARY OF THE INVENTION

A motor according to a preferred embodiment of the present inventionincludes a stationary portion and a rotating portion. The stationaryportion includes a stator. The rotating portion includes a rotor magnet.The rotating portion is rotatably supported by the stationary portionand a lubricating oil is provided between the rotating portion and thestationary portion. The stationary portion includes a shaft portion andan upper thrust portion. The shaft portion is centered on a central axisextending in a vertical direction. The upper thrust portion is arrangedto extend radially outward from an upper portion of the shaft portion.The upper thrust portion includes a first outer circumferential surfaceand a second outer circumferential surface. The first outercircumferential surface is tubular, and is arranged radially outside theupper thrust portion. The second outer circumferential surface istubular, and is arranged above the first outer circumferential surface.The rotating portion includes a sleeve portion, a tubular portion, andan annular cover portion. The sleeve portion is arranged opposite to anouter circumferential surface of the shaft portion and a lower surfaceof the upper thrust portion. The tubular portion is arranged to extendupward from an outer edge portion of the sleeve portion, and arrangedopposite to an outer circumferential surface of the upper thrustportion. The annular cover portion is arranged to extend radially inwardfrom the tubular portion. The lower surface of the upper thrust portionand an upper surface of the sleeve portion are arranged to togetherdefine an upper thrust gap therebetween, and the lubricating oil isarranged in the upper thrust gap. The outer circumferential surface ofthe upper thrust portion and an inner circumferential surface of thetubular portion are arranged to together define an upper seal portiontherebetween, and the upper thrust gap is arranged to be incommunication with the upper seal portion. The upper seal portionincludes a surface of the lubricating oil located therein. The annularcover portion includes a plate portion and an inner annular projectingportion. The plate portion is arranged to extend radially. The innerannular projecting portion is arranged radially inward of the plateportion, and is arranged to project upward or downward. An innercircumferential surface of the inner annular projecting portion isarranged above the inner circumferential surface of the tubular portion.The inner circumferential surface of the inner annular projectingportion and the second outer circumferential surface are arrangedopposite to each other with an axially extending gap interveningtherebetween. The gap is arranged to have a radial width smaller than amaximum width of the upper seal portion. According to a preferredembodiment of the present invention, a reduction in evaporation of thelubricating oil is achieved.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a storage disk drive according to afirst preferred embodiment of the present invention.

FIG. 2 is a cross-sectional view of a motor according to the firstpreferred embodiment.

FIG. 3 is a cross-sectional view of a bearing mechanism according to thefirst preferred embodiment.

FIG. 4 is a cross-sectional view of the bearing mechanism according tothe first preferred embodiment.

FIG. 5 is a cross-sectional view of a sleeve portion according to thefirst preferred embodiment.

FIG. 6 is a bottom view of a shaft portion and an upper thrust portionaccording to the first preferred embodiment.

FIG. 7 is a plan view of a lower thrust portion according to the firstpreferred embodiment.

FIG. 8 is a cross-sectional view of the bearing mechanism according tothe first preferred embodiment.

FIG. 9 is a bottom view of an inner tubular portion of a bearingmechanism according to another preferred embodiment of the presentinvention.

FIG. 10 is a cross-sectional view of a bearing mechanism in a motoraccording to a second preferred embodiment of the present invention.

FIG. 11 is a cross-sectional view of a motor according to a thirdpreferred embodiment of the present invention.

FIG. 12 is a cross-sectional view of a bearing mechanism according tothe third preferred embodiment.

FIG. 13 is a cross-sectional view of a seal cap according to the thirdpreferred embodiment.

FIG. 14 is a bottom view of the seal cap according to the thirdpreferred embodiment.

FIG. 15 is a diagram illustrating a seal cap according to anotherpreferred embodiment of the present invention.

FIG. 16 is a diagram illustrating an upper hub tubular portion accordingto another preferred embodiment of the present invention.

FIG. 17 is a diagram illustrating an upper hub tubular portion accordingto yet another preferred embodiment of the present invention.

FIG. 18 is a cross-sectional view of a storage disk drive according to afourth preferred embodiment of the present invention.

FIG. 19 is a diagram illustrating a seal cap according to yet anotherpreferred embodiment of the present invention.

FIG. 20 is a diagram illustrating a seal cap according to yet anotherpreferred embodiment of the present invention.

FIG. 21 is a diagram illustrating a seal cap according to yet anotherpreferred embodiment of the present invention.

FIG. 22 is a diagram illustrating a seal cap according to yet anotherpreferred embodiment of the present invention.

FIG. 23 is a diagram illustrating a shaft portion and an upper thrustportion according to another preferred embodiment of the presentinvention.

FIG. 24 is a diagram illustrating a shaft portion and an upper thrustportion according to yet another preferred embodiment of the presentinvention.

FIG. 25 is a bottom view of a shaft portion and an upper thrust portionaccording to yet another preferred embodiment of the present invention.

FIG. 26 is a plan view of a lower thrust portion according to anotherpreferred embodiment of the present invention.

FIG. 27 is a cross-sectional view of a motor according to anotherpreferred embodiment of the present invention.

FIG. 28 is a cross-sectional view illustrating an upper thrust portion,a tubular portion, an annular cover portion, and their vicinitiesaccording to a preferred embodiment of the present invention.

FIG. 29 is a cross-sectional view illustrating an upper thrust portion,a tubular portion, an annular cover portion, and their vicinitiesaccording to a preferred embodiment of the present invention.

FIG. 30 is a cross-sectional view illustrating an upper thrust portion,a tubular portion, an annular cover portion, and their vicinitiesaccording to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is assumed herein that an upper side and a lower side in a directionparallel or substantially parallel to a central axis of a motor arereferred to as an “upper side” and a “lower side”, respectively. Notethat the terms “vertical direction”, “upper side”, “lower side”, and thelike as used herein are not meant to indicate relative positions ordirections of different members or portions when actually installed in adevice. Also note that directions parallel to or substantially parallelto the central axis are referred to by the term “axial direction”,“axial”, or “axially”, that directions radiating from the central axisare simply referred to by the term “radial direction”, “radial”, or“radially”, and that a circumferential direction about the central axisis simply referred to by the term “circumferential direction”,“circumferential”, or “circumferentially”.

First Preferred Embodiment

FIG. 1 is a cross-sectional view of a storage disk drive 1 including aspindle motor (hereinafter referred to simply as a “motor”) 12 accordingto a first preferred embodiment of the present invention. The storagedisk drive 1 is preferably a so-called hard disk drive. The storage diskdrive 1 preferably includes three disks 11, the motor 12, an accessportion 13, and a housing 14, for example. The motor 12 is arranged torotate the disks 11, on which information is stored. The access portion13 is arranged to read and/or write information from or to the disks 11.In other words, the access portion 13 may be arranged to perform atleast one of reading and writing of information from or to the disks 11.

The housing 14 preferably includes a lower housing member 141 and anupper plate member 142. The lower housing member 141 is in the shape ofa box without a lid. The upper plate member 142 preferably has a flatshape, such as that of a plate. The disks 11, the motor 12, and theaccess portion 13 are arranged inside the lower housing member 141. Theupper plate member 142 is fitted to the lower housing member 141 todefine the housing 14. An interior space of the storage disk drive 1 ispreferably a clean space with no dirt or dust, or only an extremelysmall amount of dirt or dust. In the present preferred embodiment, theinterior space of the storage disk drive 1 is filled with air. Note thatthe interior space of the storage disk drive 1 may alternatively befilled with helium gas, hydrogen gas, a mixture of either or both ofthese gases and air, or any other desirable gas.

The three disks 11 are fixed to a rotor hub of the motor 12 through aclamper 151 and spacers 152 such that the disks 11 are arranged atregular intervals in a direction parallel or substantially parallel to acentral axis J1 of the motor 12. The access portion 13 includes sixheads 131, six arms 132, and a head actuator mechanism 133. Each of theheads 131 is arranged in close proximity to one of the disks 11 to readand write information from or to the disk 11. Note that the head 131 maybe arranged to perform at least one of the reading and writing ofinformation from or to the disk 11. Each of the arms 132 is arranged tosupport an associated one of the heads 131. The head actuator mechanism133 is arranged to move each of the arms 132 to move an associated oneof the heads 131 relative to an associated one of the disks 11. Theabove mechanism enables the head 131 to make access to a desiredlocation on the disk 11 with the head 131 being arranged in closeproximity to the rotating disk 11. Note that the number of disks 11 isnot limited to three, but may instead be one, two, or any otherdesirable number greater than three.

FIG. 2 is a cross-sectional view of the motor 12. The motor 12 is anouter-rotor motor. The motor 12 includes a stationary portion 2, whichis a stationary assembly, and a rotating portion 3, which is a rotatingassembly. In FIG. 2, a fluid dynamic bearing mechanism (hereinafterreferred to as a “bearing mechanism”) defined by a portion of thestationary portion 2 and a portion of the rotating portion 3 isindicated by reference numeral “4”. The rotating portion 3 is supportedthrough a lubricating oil 45 such that the rotating portion 3 isrotatable about the central axis J1 of the motor 12 with respect to thestationary portion 2.

The stationary portion 2 preferably includes a base plate 21, i.e., abase portion, a stator 22, a shaft portion 41, an upper thrust portion42, and a lower thrust portion 43. The base plate 21 and the lowerhousing member 141 illustrated in FIG. 1 are preferably integrallydefined by a single monolithic member and define a portion of thehousing 14. The stator 22 is fixed to a circumference of a cylindricalholder 211 defined in the base plate 21. A hole portion is definedinside the holder 211. Note that the base plate 21 and the lower housingmember 141 may be defined by separate members. The shaft portion 41 andthe upper thrust portion 42 are defined by a single monolithic member.The shaft portion 41 includes a screw hole defined in an upper portionthereof. Referring to FIG. 1, a central portion 143 of the upper platemember 142 is recessed axially downward. Hereinafter, the centralportion 143 will be referred to as a “plate central portion 143”. Ascrew 161, for example, is preferably inserted into a through holedefined in the plate central portion 143 and the screw hole of the shaftportion 41, so that the plate central portion 143 and the shaft portion41 are fixed to each other. A lower surface of the plate central portion143 is arranged in direct contact with an upper surface of the upperthrust portion 42, whereby the upper plate member 142 is securely fixedto the motor 12. Moreover, because the shaft portion 41 and the upperthrust portion 42 are defined by a single monolithic member, animprovement in strength is achieved with which the upper plate member142 is joined to the motor 12.

Referring to FIG. 2, the rotating portion 3 includes a rotor hub 31 anda rotor magnet 32. The rotor hub 31 preferably includes a substantiallycylindrical sleeve portion 5, a cover portion 311, and a cylindricalportion 312. The cover portion 311 is arranged to extend radiallyoutward from an upper portion of the sleeve portion 5. The cylindricalportion 312 is arranged to extend axially downward from an outer edgeportion of the cover portion 311. The rotor magnet 32 is fixed to aninside of the cylindrical portion 312. The rotor magnet 32 is arrangedradially opposite the stator 22. The rotating portion 3 is arranged tobe rotated in response to a torque that is generated between the stator22 and the rotor magnet 32. Note that, if so desired, the sleeve portion5 may be defined by a member separate from the cover portion 311 and thecylindrical portion 312. In this case, the sleeve portion 5 is fixed tothe cover portion 311.

FIG. 3 is an enlarged view of the bearing mechanism 4. The bearingmechanism 4 preferably includes the shaft portion 41, the upper thrustportion 42, the lower thrust portion 43, the sleeve portion 5, anannular seal cap 44, i.e., a cap member, and the lubricating oil 45. Asmentioned above, each of the shaft portion 41, the upper thrust portion42, and the lower thrust portion 43 preferably defines a portion of thestationary portion 2, while each of the sleeve portion 5 and the sealcap 44 defines a portion of the rotating portion 3. The shaft portion 41is, for example, press fitted so as to be fixed to a hole portiondefined inside the lower thrust portion 43. The shaft portion 41 isarranged to orient in the vertical direction along the central axis J1.The upper thrust portion 42 includes an upper plate portion which ispreferably flat, such that it possesses the shape of a plate, andarranged to extend radially outward from the upper portion of the shaftportion 41. The shaft portion 41 and the upper thrust portion 42 arepreferably made of stainless steel or the like, for example. An outercircumferential surface 422 of the upper thrust portion 42 includes aninclined surface that is angled in a radially inward direction withincreasing height. The upper thrust portion 42 preferably includes adownward recessed shoulder portion 423 defined in an outer edge portionof the upper surface thereof.

The lower thrust portion 43 preferably includes a lower plate portion431 and an outer tubular portion 432. The lower thrust portion 43preferably is made of copper, high-strength brass, or the like, forexample. The lower plate portion 431 is arranged to extend radiallyoutward from a lower portion of the shaft portion 41. The outer tubularportion 432 is arranged to extend upward from an outer edge portion ofthe lower plate portion 431. An upper portion of an outercircumferential surface of the outer tubular portion 432 includes aninclined surface 433 that is angled in the radially inward directionwith decreasing height.

In assembling the motor 12, a lower portion of the outer circumferentialsurface of the outer tubular portion 432 is fixed to an innercircumferential surface of the holder 211 of the base plate 21 through,for example, an adhesive. In comparison to press fitting, the abovemethod enables the vertical positioning of the outer tubular portion 432relative to the base plate 21 to be achieved with greater precision,whereby improved precision in the height of the motor 12 is achieved.

The sleeve portion 5 includes an inner tubular portion 51 and a flangeportion 52. The sleeve portion 5 is preferably made of stainless steel,aluminum, copper, or the like, for example. The inner tubular portion 51is arranged in a substantially cylindrical space defined between theouter tubular portion 432 and the shaft portion 41. The flange portion52 is arranged to project radially outward from an upper portion of theinner tubular portion 51. The axial thickness of the flange portion 52is preferably a half or less than a half of the axial dimension of aninner circumferential surface 511 of the inner tubular portion 51, forexample. Both an upper surface 521 and a lower surface 522 of the flangeportion 52 are preferably arranged to be substantially perpendicular tothe central axis J1. The flange portion 52 includes a communicating hole61 arranged to extend through the flange portion 52 in the verticaldirection. The number of communicating holes 61 preferably is one, forexample, in the present preferred embodiment. However, if so desired,two or more communicating holes 61 could also be defined in the flangeportion.

The cover portion 311 of the rotor hub 31 includes an upper hub tubularportion 53 and a lower hub tubular portion 54. The upper hub tubularportion 53 is arranged substantially in the shape of a cylinder, and isarranged to extend axially upward from an outer edge portion of thesleeve portion 5, i.e., an outer edge portion of the flange portion 52.The upper hub tubular portion 53 is arranged radially outward of theupper thrust portion 42. An inner circumferential surface 531 of theupper hub tubular portion 53 includes a portion that is angled in theradially inward direction with increasing height. Hereinafter, the upperhub tubular portion 53 and the seal cap 44, which are arranged above theouter edge portion of the flange portion 52 and each of which defines aportion of the rotating portion 3, will be collectively referred to asan “upper hub annular portion 591”.

The lower hub tubular portion 54 is arranged substantially in the shapeof a cylinder, and is arranged to extend downward from the outer edgeportion of the flange portion 52. The lower hub tubular portion 54 isarranged radially outward of the outer tubular portion 432 of the lowerthrust portion 43. An inner circumferential surface 541 of the lower hubtubular portion 54 includes a portion that is angled in the radiallyinward direction with decreasing height. Note that the upper and lowerhub tubular portions 53 and 54 may be defined by members separate fromthe flange portion 52 or the cover portion 311.

The seal cap 44 preferably includes a cap cylindrical portion 441 and acap cover portion 442. The cap cylindrical portion 441 is centered onthe central axis J1. The cap cover portion 442 is substantially annular,and is arranged to extend radially inward from the cap cylindricalportion 441. The cap cylindrical portion 441, which is an outer edgeportion of the seal cap 44, is fitted to the upper hub tubular portion53, whereby the seal cap 44 is attached to the sleeve portion 5. Whenthe seal cap 44 is attached to the upper hub tubular portion 53, the capcylindrical portion 441 is arranged in direct radial contact with anouter circumferential surface of the upper hub tubular portion 53, andthe cap cover portion 442 is arranged in axial contact with an uppersurface of the upper hub tubular portion 53. The cap cylindrical portion441 and the upper hub tubular portion 53 together define a tubularportion of the upper hub annular portion 591 which is arranged to extendupward from the outer edge portion of the flange portion 52. Inaddition, the cap cover portion 442 defines an annular cover portion ofthe upper hub annular portion 591 which is arranged to extend radiallyinward from the tubular portion. A radially inner portion of the capcover portion 442 is arranged above a bottom portion of the shoulderportion 423.

Referring to FIG. 2, the rotating portion 3, which includes the sleeveportion 5, is arranged to rotate through the lubricating oil 45 withrespect to the shaft portion 41, the upper thrust portion 42, and thelower thrust portion 43 while the motor 12 is driven.

FIG. 4 is an enlarged view of an upper portion of the bearing mechanism4. An outer circumferential surface 411 of the shaft portion 41 isarranged radially opposite the inner circumferential surface 511 of theinner tubular portion 51 of the sleeve portion 5. A radial gap 62 isdefined between the shaft portion 41 and the inner tubular portion 51.The radial width of the radial gap 62 is preferably in the range ofabout 2 μm to about 4 μm, for example. Referring to FIG. 3, an axial gap63 is defined between a lower end of the inner tubular portion 51 andthe lower plate portion 431. Hereinafter, the gap 63 will be referred toas a “lower end gap 63”. Note that, in the present preferred embodiment,the radial gap 62 corresponds to a first gap.

Referring to FIG. 4, a gap 64 in the shape of a cylinder is definedbetween an outer circumferential surface 512 of the inner tubularportion 51 and an inner circumferential surface 434 of the outer tubularportion 432. Hereinafter, the gap 64 will be referred to as a“cylindrical gap 64”. Referring to FIG. 3, the cylindrical gap 64 isarranged in communication with the radial gap 62 through the lower endgap 63. The radial width of the cylindrical gap 64 is preferably greaterthan the radial width of the radial gap 62 and smaller than the diameterof the communicating hole 61. Note that, in the present preferredembodiment, the cylindrical gap 64 corresponds to a second gap.

Referring to FIG. 4, a gap 651 is defined between a region of the uppersurface 521 of the flange portion 52 which is radially inward of thecommunicating hole 61 and a lower surface 421 of the upper thrustportion 42, which is arranged axially opposite the upper surface 521.Hereinafter the gap 651 will be referred to as an “upper thrust gap651”. In addition, a gap 652 is defined between a region of the lowersurface 522 of the flange portion 52 which is radially inward of thecommunicating hole 61 and an upper surface 435 of the outer tubularportion 432. Hereinafter, the gap 652 will be referred to as a “lowerthrust gap 652”. The upper and lower thrust gaps 651 and 652 arearranged in communication with each other through the communicating hole61. In the bearing mechanism 4, the radial gap 62, the lower end gap 63,the cylindrical gap 64, the upper and lower thrust gaps 651 and 652, andthe communicating hole 61 are arranged from a radial inside to a radialoutside in this order. Note that, in the present preferred embodiment,the lower thrust gap 652 corresponds to a third gap.

The inner circumferential surface 531 of the upper hub tubular portion53 is arranged radially opposite the outer circumferential surface 422of the upper thrust portion 42. A gap 661 is defined between the upperhub tubular portion 53 and the upper thrust portion 42. The upper thrustgap 651 is arranged in communication with the gap 661. The gap 661 ispreferably arranged radially outward of the radial gap 62, the upperthrust gap 651, and the communicating hole 61. The gap 661 is arrangedto gradually increase in width with increasing height, that is, withdecreasing distance from an upper end opening of the gap 661.Hereinafter, the gap 661 will be referred to as an “upper seal gap 661”.In addition, the upper seal gap 661 is arranged to be angled toward thecentral axis J1 with increasing height. In other words, the upper sealgap 661 is arranged to be angled to the left in FIG. 4 with increasingheight. A surface of the lubricating oil 45 is located in the upper sealgap 661. The lubricating oil 45 is retained in the upper seal gap 661through capillary action. An upper seal portion 661 a arranged to retainthe lubricating oil 45 is thus defined in the upper seal gap 661. Theinner circumferential surface 531 and the outer circumferential surface422 are preferably coated with oil-repellent films 86 above the surfaceof the lubricating oil 45 in the upper seal gap 661. The upper endopening of the upper seal gap 661 is covered with the cap cover portion442 of the seal cap 44.

The inner circumferential surface 541 of the lower hub tubular portion54 is arranged radially opposite the inclined surface 433 of the outertubular portion 432. A gap 662 extending downward is defined between thelower hub tubular portion 54 and the outer tubular portion 432. The gap662 is arranged radially outward of the radial gap 62, the lower end gap63, the cylindrical gap 64, the lower thrust gap 652, and thecommunicating hole 61. The gap 662 is arranged to gradually increase inwidth with decreasing height, that is, with decreasing distance from alower end opening of the gap 662. Hereinafter, the gap 662 will bereferred to as a “lower seal gap 662”. In addition, the lower seal gap662 is arranged to be angled toward the central axis J1 with decreasingheight. That is, the lower seal gap 662 is arranged to be inclined tothe left in FIG. 4 with decreasing height. A surface of the lubricatingoil 45 is located in the lower seal gap 662. The lubricating oil 45 isretained in the lower seal gap 662 through capillary action. A lowerseal portion 662 a arranged to retain the lubricating oil 45 is definedin the lower seal gap 662. The inner circumferential surface 541 and theinclined surface 433 are coated with oil-repellent films 86 below thesurface of the lubricating oil 45 in the lower seal gap 662. The sameholds true for other preferred embodiments described below. In thebearing mechanism 4, the upper and lower seal gaps 661 and 662 arearranged in communication with each other through the communicating hole61.

The axial distance between the surface of the lubricating oil 45 in theupper seal portion 661 a and the surface of the lubricating oil 45 inthe lower seal portion 662 a is shorter than the axial length of theradial gap 62. Moreover, the length of the communicating hole 61 isshorter than the axial distance between the surface of the lubricatingoil 45 in the upper seal portion 661 a and the surface of thelubricating oil 45 in the lower seal portion 662 a. It is assumed herethat the distance between the surface of the lubricating oil 45 in theupper seal portion 661 a and the surface of the lubricating oil 45 inthe lower seal portion 662 a refers to the distance between an upper endof the surface of the lubricating oil 45 in the upper seal portion 661 aand a lower end of the surface of the lubricating oil 45 in the lowerseal portion 662 a.

Referring to FIG. 3, the radially outside diameter of the upper seal gap661 is preferably substantially equal to the radially outside diameterof the lower seal gap 662. This makes it possible to arrange thecommunicating hole 61 to extend in parallel or substantially in parallelwith the central axis J1. It is assumed here that the outside diameterof the upper seal gap 661 refers to the outside diameter of an innermostportion of the upper seal gap 661, and that the outside diameter of thelower seal gap 662 refers to the outside diameter of an innermostportion of the lower seal gap 662.

In the bearing mechanism 4, the communicating hole 61 and a space 6extending from the upper seal gap 661 to the lower seal gap 662 throughthe upper thrust gap 651, the radial gap 62, the lower end gap 63, thecylindrical gap 64, and the lower thrust gap 652 are continuously filledwith the lubricating oil 45. When the bearing mechanism 4 isconstructed, the lubricating oil 45 is fed into the bearing mechanism 4through the lower seal gap 662 with the lower seal gap 662 arranged toface axially upward in the direction of gravity. It is possible tocontrol the amount of the lubricating oil 45 by visually identifying theheight of the surface of the lubricating oil 45 in the lower seal gap662.

Note that the visual identification may be conducted either with eyesalone or with a magnified view of the lower seal gap 662 with the aid ofa device such as, for example, a microscope. Also note that the visualidentification may be conducted with a magnified image of the lower sealgap 662 shown on a screen with the aid of a device.

FIG. 5 is a cross-sectional view of the sleeve portion 5. In FIG. 5, theshape of the sleeve portion 5 beyond a cross section thereof is alsodepicted. The inner tubular portion 51 includes an upper radial dynamicpressure groove array 711 and a lower radial dynamic pressure groovearray 712. The upper radial dynamic pressure groove array 711 is definedin a portion of the inner circumferential surface 511 which is on anupper side of a substantial axial middle thereof. The lower radialdynamic pressure groove array 712 is defined in a portion of the innercircumferential surface 511 which is on a lower side of the substantialaxial middle thereof. In FIG. 5, dynamic pressure grooves are indicatedby cross-hatching. Also in other figures referenced below, dynamicpressure grooves are indicated by cross-hatching. The upper radialdynamic pressure groove array 711 is includes a collection of groovesarranged in, for example, a herringbone pattern, that is, a collectionof a plurality of grooves each of which is arranged substantially in theshape of the letter “V” in horizontal orientation along acircumferential direction of the inner circumferential surface 511. Theaxial dimension of an upper portion of the upper radial dynamic pressuregroove array 711 is preferably arranged to be greater than that of alower portion of the upper radial dynamic pressure groove array 711.Hereinafter, the upper portion and the lower portion of the upper radialdynamic pressure groove array 711 will be referred to as a “groove upperportion 711 a” and a “groove lower portion 711 b”, respectively. Thelower radial dynamic pressure groove array 712 is also defined bygrooves arranged in the herringbone pattern. The axial dimension of agroove upper portion 712 a of the lower radial dynamic pressure groovearray 712 is arranged to be smaller than that of a groove lower portion712 b of the lower radial dynamic pressure groove array 712.

The lower thrust gap 652 illustrated in FIG. 4 is arranged at a levelhigher than that of an upper end of the groove upper portion 712 a ofthe lower radial dynamic pressure groove array 712. In the radial gap62, a radial dynamic pressure bearing 81 arranged to generate a radialfluid dynamic pressure acting on the lubricating oil 45 is definedthrough the upper and lower radial dynamic pressure groove arrays 711and 712. Hereinafter, an upper dynamic pressure bearing portioncorresponding to the upper radial dynamic pressure groove array 711 willbe referred to as an “upper radial dynamic pressure bearing portion811”, while a lower dynamic pressure bearing portion corresponding tothe lower radial dynamic pressure groove array 712 will be referred toas a “lower radial dynamic pressure bearing portion 812”. The lowerradial dynamic pressure bearing portion 812 is arranged to overlap in aradial direction with a fixing region 436 where the lower portion of theouter circumferential surface of the outer tubular portion 432 and theholder 211 of the base plate 21 illustrated in FIG. 3 are fixed to eachother.

Note that it is enough that the level of the lower thrust gap 652 shouldbe arranged to be higher than that of the upper end of at least one ofthe dynamic pressure grooves constituting the lower radial dynamicpressure groove array 712. Also note that the level of the lower thrustgap 652 may be arranged to be higher than that of the upper end of eachof all the dynamic pressure grooves constituting the lower radialdynamic pressure groove array 712. These arrangements fall within thescope of preferred embodiments of the present invention.

FIG. 6 is a bottom view of the shaft portion 41 and the upper thrustportion 42. In FIG. 6, a position corresponding to the communicatinghole 61 is indicated by a chain double-dashed line. The same holds truefor FIG. 7. The lower surface 421 of the upper thrust portion 42includes an upper thrust dynamic pressure groove array 721 arranged in aspiral pattern defined therein. The upper thrust dynamic pressure groovearray 721 is arranged radially inward of a circle 731 which is centeredon the central axis J1 and which touches an upper end opening of thecommunicating hole 61 at a radially outer point. Note that, in the casewhere the upper end opening is provided with a chamfer, the upper thrustdynamic pressure groove array 721 is arranged radially inward of acircle which is centered on the central axis J1 and which touches thechamfer at a radially outer point. In addition, an outer circumferentialportion of the upper thrust dynamic pressure groove array 721 isarranged to overlap with the upper end opening of the communicating hole61. In the upper thrust gap 651 illustrated in FIG. 4, a dynamicpressure bearing portion 821, which is a dynamic pressure generationportion arranged to generate a fluid dynamic pressure acting on thelubricating oil 45 in a thrust direction, is defined through the upperthrust dynamic pressure groove array 721. Hereinafter, the dynamicpressure bearing portion 821 will be referred to as an “upper thrustdynamic pressure bearing portion 821”.

Note that it is enough that at least one of the dynamic pressure groovesdefining the upper thrust dynamic pressure groove array 721 should bearranged radially inward of the circle 731. Also note that all of thedynamic pressure grooves defining the upper thrust dynamic pressuregroove array 721 may be arranged radially inward of the circle 731.These arrangements fall within the scope of preferred embodiments of thepresent invention.

FIG. 7 is a plan view of the lower thrust portion 43. The upper surface435 of the outer tubular portion 432 includes a lower thrust dynamicpressure groove array 722 arranged in the spiral pattern definedtherein. The lower thrust dynamic pressure groove array 722 is arrangedradially inward of a circle 732 which is centered on the central axis J1and which touches a lower end opening of the communicating hole 61 at aradially outer point. Note that, in the case where the lower end openingis provided with a chamfer, the lower thrust dynamic pressure groovearray 722 is arranged radially inward of a circle which is centered onthe central axis J1 and which touches the chamfer at a radially outerpoint. In addition, an outer circumferential portion of the lower thrustdynamic pressure groove array 722 is arranged to overlap with the lowerend opening of the communicating hole 61. In the lower thrust gap 652illustrated in FIG. 4, a dynamic pressure bearing portion 822, which isa dynamic pressure generation portion arranged to generate a fluiddynamic pressure acting on the lubricating oil 45 in the thrustdirection, is defined through the lower thrust dynamic pressure groovearray 722. Hereinafter, the dynamic pressure bearing portion 822 will bereferred to as a “lower thrust dynamic pressure bearing portion 822”.

Note that it is enough that at least one of the dynamic pressure groovesdefining the lower thrust dynamic pressure groove array 722 should bearranged radially inward of the circle 732. Also note that all of thedynamic pressure grooves defining the lower thrust dynamic pressuregroove array 722 may be arranged radially inward of the circle 732.These arrangements fall within the scope of preferred embodiments of thepresent invention.

Even when the upper thrust dynamic pressure groove array 721 is arrangedto overlap with the upper end opening of the communicating hole 61, andthe lower thrust dynamic pressure groove array 722 is arranged tooverlap with the lower end opening of the communicating hole 61, adifference in pressure between an interior and an exterior of thecommunicating hole 61 is eliminated through the inclusion of a regionwhere neither the upper thrust dynamic pressure groove array 721 nor thelower thrust dynamic pressure groove array 722 is provided. As a result,a reduction in the difference in pressure between the upper and lowerseal portions 661 a and 662 a is achieved.

While the motor 12 is driven, the inner tubular portion 51 of the sleeveportion 5 is supported by the radial dynamic pressure bearing 81 in theradial direction with respect to the shaft portion 41, while the flangeportion 52 is supported by a thrust dynamic pressure bearing defined bythe upper and lower thrust dynamic pressure bearing portions 821 and 822in the thrust direction with respect to the upper thrust portion 42 andthe outer tubular portion 432.

At this time, each of the upper and lower radial dynamic pressure groovearrays 711 and 712 illustrated in FIG. 5 generates a dynamic pressure bypumping the lubricating oil 45 to a middle portion thereof. As describedabove, the groove lower portion 711 b of the upper radial dynamicpressure groove array 711 is arranged to be shorter than the grooveupper portion 711 a thereof, while the groove upper portion 712 a of thelower radial dynamic pressure groove array 712 is arranged to be shorterthan the groove lower portion 712 b thereof. The radial dynamic pressurebearing 81 as a whole is arranged to generate little pressure acting onthe lubricating oil 45 in the vertical direction.

Meanwhile, in the upper thrust gap 651 illustrated in FIG. 4, a pressureacting on the lubricating oil 45 in the direction of the shaft portion41 is generated by the upper thrust dynamic pressure bearing portion821. The pressure on the lubricating oil 45 is thereby increased in anaxially upper portion of the radial gap 62 and a radially inner portionof the upper thrust gap 651, whereby generation of an air bubble isprevented therein.

In the lower thrust dynamic pressure bearing portion 822, a pressureacting on the lubricating oil 45 in the direction of the cylindrical gap64 is generated. The pressure on the lubricating oil 45 is increased inan axially lower portion of the radial gap 62, the lower end gap 63, thecylindrical gap 64, and a radially inner portion of the lower thrust gap652, whereby generation of an air bubble is prevented in the cylindricalgap 64 and the lower end gap 63. As described above, in the motor 12, apressure is applied to the lubricating oil 45 throughout an entirecirculation channel of the lubricating oil 45 except for thecommunicating hole 61, so that a sufficient bearing performance of thebearing mechanism 4 is ensured.

Next, the structure of the upper seal gap 661 and its vicinity withinthe motor 12 will now be described below. Referring to FIG. 8, theshoulder portion 423 of the upper thrust portion 42 preferably includesan inner cylindrical surface 741, an outer annular surface 742, and anannular groove portion 743. The inner cylindrical surface 741 issubstantially cylindrical, and is arranged radially inward of the outercircumferential surface 422 to extend in the axial direction. The innercylindrical surface 741 is arranged radially outward of the radialdynamic pressure bearing 81 illustrated in FIG. 4. An upper end of theinner cylindrical surface 741 is arranged at a level higher than that ofan upper end of the outer circumferential surface 422. The outer annularsurface 742 is arranged radially outward of the inner cylindricalsurface 741, and radially inward of the outer circumferential surface422. The outer annular surface 742 is an annular surface perpendicularor substantially perpendicular to the central axis J1. The outer annularsurface 742 is arranged at an axial level lower than that of the upperend of the inner cylindrical surface 741. The groove portion 743 isarranged between the inner cylindrical surface 741 and the outer annularsurface 742. The groove portion 743 is recessed axially downwardrelative to the outer annular surface 742. Note that the shoulderportion 423 does not cause a significant decrease in rigidity of theupper thrust portion 42 because the upper thrust portion 42 is arrangedto have a sufficient thickness between the lower surface 421 and acombination of the outer annular surface 742 and a bottom surface of thegroove portion 743.

A radially extending gap 663 a, which is annular and arranged to extendradially, is defined between a lower surface of the cap cover portion442 of the seal cap 44 and the outer annular surface 742. An axiallyextending gap 663 b, which is annular, is defined between a radiallyinner edge 443 of the cap cover portion 442 and the inner cylindricalsurface 741. An upper portion of the upper seal gap 661 is continuouswith the radially extending gap 663 a. The radially extending gap 663 ais continuous with the axially extending gap 663 b through a gap 663 cdefined between the cap cover portion 442 and the groove portion 743.Hereinafter, the gap 663 c will be referred to as a “groove portion gap663 c”. The axially extending gap 663 b is arranged to open into a spaceabove the upper thrust portion 42. The upper seal gap 661 is thusarranged in communication with the space above the upper thrust portion42 through the radially extending gap 663 a, the groove portion gap 663c, and the axially extending gap 663 b. Hereinafter, the radiallyextending gap 663 a, the groove portion gap 663 c, and the axiallyextending gap 663 b will be collectively referred to as a “communicatinggap 663”. The radially extending gap 663 a is a region where thecommunicating gap 663 has a locally decreased axial width. The axiallyextending gap 663 b is a region where the communicating gap 663 has alocally decreased radial width.

The axial width of the radially extending gap 663 a is arranged to besmaller than the maximum radial width of the upper seal gap 661. Inother words, the axial width of the radially extending gap 663 a isarranged to be smaller than the radial distance between an edge 422 awhere the outer annular surface 742 and the outer circumferentialsurface 422 meet and an upper edge of a chamfer 531 a defined in aninner top portion of the upper hub tubular portion 53. Note that, in thecase where a chamfer is defined between the outer annular surface 742and the outer circumferential surface 422, the maximum radial width ofthe upper seal gap 661 refers to the radial distance between an upperedge of this chamfer and the upper edge of the chamfer 531 a of theupper hub tubular portion 53.

An excessively large axial width of the radially extending gap 663 a andan excessively large radial width of the axially extending gap 663 bwill lead to a significant reduction in an effect of reducing axial andradial flows of air therein. On the other hand, an excessively smallaxial width of the radially extending gap 663 a and an excessively smallradial width of the axially extending gap 663 b will lead to anincreased probability of contacting between the seal cap 44 and theupper thrust portion 42. Therefore, the axial width of the radiallyextending gap 663 a is preferably set at an appropriate value to reducethe axial flow of air therein, and the radial width of the axiallyextending gap 663 b is preferably set at an appropriate value to reducethe radial flow of air therein, and also to prevent a contact of theseal cap 44 with the upper thrust portion 42.

For example, the axial width of the radially extending gap 663 a ispreferably arranged in the range of about 0.05 mm to about 0.2 mm.Specifically, the axial width of the radially extending gap 663 a ismore preferably arranged in the range of about 0.05 mm to about 0.1 mm,for example. The radial width of the axially extending gap 663 b ispreferably arranged in the range of about 0.05 mm to about 0.2 mm, forexample. As with the axial width of the radially extending gap 663 a,the radial width of the axially extending gap 663 b is arranged to besmaller than the maximum radial width of the upper seal gap 661.Moreover, the axial width of the radially extending gap 663 a ispreferably arranged to be smaller than the radial width of the axiallyextending gap 663 b.

In the motor 12, the communicating gap 663 is arranged to have alabyrinth structure, including a radially extending gap and an axiallyextending gap, and therefore, an air containing an evaporatedlubricating oil in the upper seal gap 661 is prevented from traveling toan outside of the motor 12 therethrough. In particular, because thecommunicating gap 663 is arranged radially inward of the upper seal gap661, a centrifugal force acting on an air in the communicating gap 663in the direction of the upper seal gap 661 is generated while the motor12 is driven. This contributes to an additional prevention of the travelof the air containing the evaporated lubricating oil to the outside ofthe motor 12. Note that the motor 12 has an increased resistance againsta flow of air in the communicating gap compared with a motor in which acommunicating gap in communication with the outside of the motor isarranged radially outward of the seal gap. Furthermore, acircumferential air current is generated in the axially extending gap663 b, and this contributes to preventing air from traveling between thespace above the upper thrust portion 42 and the groove portion gap 663c. It is easy to secure a sufficient radial dimension of the radiallyextending gap 663 a in the communicating gap 663. The radially extendinggap 663 a having a small width and a large radial dimension makes itpossible to secure a sufficient resistance against the flow of airtherein.

The motor 12 according to the first preferred embodiment has beendescribed above. The provision of the radially extending gap 663 a andthe axially extending gap 663 b in the motor 12 contributes to reducingevaporation of the lubricating oil 45, and achieving an improvement in alife of the motor 12. Because the upper seal portion 661 a is arrangedin a radially outer portion of the bearing mechanism 4, it is possibleto secure a sufficient space to arrange the communicating gap 663 in aradially inner portion of the bearing mechanism 4.

The provision of the groove portion 743 in the shoulder portion 423 ofthe upper thrust portion 42 makes it possible to arrange the inner edge443 of the seal cap 44 in closer proximity to the inner cylindricalsurface 741, and makes it easier to define the axially extending gap 663b, than in the case where a curved surface smoothly joining the innercylindrical surface 741 and the outer annular surface 742 to each otheris defined instead of the groove portion 743.

In the bearing mechanism 4, the axial distance between the surface ofthe lubricating oil 45 in the upper seal portion 661 a and the surfaceof the lubricating oil 45 in the lower seal portion 662 a is shorterthan the axial length of the radial dynamic pressure bearing 81. Theaxial length of the radial dynamic pressure bearing 81 refers to thedistance between an upper end and a lower end of the radial dynamicpressure bearing 81. More specifically, the axial length of the radialdynamic pressure bearing 81 refers to the distance between an upper endof the groove upper portion 711 a of the upper radial dynamic pressuregroove array 711 and a lower end of the groove lower portion 712 b ofthe lower radial dynamic pressure groove array 712. Note that a portionthat does not contribute to the function of the dynamic pressure bearingmay exist between the upper and lower ends. The same holds true forother preferred embodiments of the present invention described below. Areduction in a difference in pressure between the upper seal portion 661a and the lower seal portion 662 a is achieved by arranging the upperseal portion 661 a and the lower seal portion 662 a to be closer to eachother in the axial direction as described above. This prevents a leakageof the lubricating oil 45.

Moreover, the axial length of the communicating hole is shorter than theaxial distance between the upper seal portion 661 a and the lower sealportion 662 a. This contributes to reducing the amount of thelubricating oil 45 arranged in the communicating hole 61, and at thesame time to reducing channel resistance. A reduction in a difference inpressure between the upper and lower seal gaps 661 and 662 owing toinfluence of channel resistance and gravity acting on the lubricatingoil 45 in the communicating hole 61 is achieved. This contributes toreducing movement of the lubricating oil 45 between the upper and lowerseal gaps 661 and 662, and further prevents leakage of the lubricatingoil 45.

Furthermore, the cylindrical gap 64, which corresponds to the secondgap, is arranged to be in communication with a lower portion of theradial gap 62, which corresponds to the first gap, while at the sametime the lower thrust gap 652, which corresponds to the third gap, isarranged axially above the lower radial dynamic pressure bearing portion812. This arrangement makes it possible to arrange the lower thrust gap652 to be closer to the upper thrust gap 651, making it easier to reducethe length of the communicating hole 61, which is arranged to make theupper and lower thrust gaps 651 and 652 in communication with eachother. As a result, the upper seal portion 661 a and the lower sealportion 662 a are arranged to be closer to each other.

The communicating hole 61 is arranged to extend in parallel orsubstantially in parallel with the central axis J1 to reduce adifference between the distance from the upper end opening of thecommunicating hole 61 to the upper seal gap 661 and the distance fromthe lower end opening of the communicating hole 61 to the lower seal gap662. This arrangement contributes to further reducing the difference inpressure between the upper and lower seal gaps 661 and 662.

Furthermore, the end opening of each of the upper and lower seal gaps661 and 662 is arranged to be angled to face the central axis J1.Therefore, during rotation of the motor 12, the lubricating oil 45 ispressed inward in each of the upper and lower seal gaps 661 and 662through a centrifugal force. This prevents a leakage of the lubricatingoil 45. As a result, designing of the motor 12 is made easier.

The upper thrust dynamic pressure groove array 721 is arranged to extendradially outward to such an extent that the outer circumferentialportion thereof overlaps with the communicating hole 61 in plan view. Asa result, a thrust dynamic pressure is efficiently obtained, and aportion of the flange portion 52 which is close to the outer edgeportion thereof is supported by the upper thrust dynamic pressurebearing portion 821. This contributes to more stable support of thesleeve portion 5. The same holds true for the lower thrust dynamicpressure groove array 722.

In the motor 12, the lower thrust gap 652 is arranged in the upperportion of the bearing mechanism 4. Accordingly, a space is securedbelow the lower thrust gap 652, and the fixing region 436 where theouter tubular portion 432 and the base plate 21 are fixed to each othercan be arranged in this space. This enables the fixing region 436 tohave a sufficient axial dimension. In the motor 12, a greater axiallength of the radial gap 62 is preferred because an increase in theaxial length of the radial dynamic pressure bearing 81 can thereby beachieved, and an improvement in rigidity of the bearing mechanism 4against an external force acting in such a direction as to tilt therotating portion 3 can also be achieved. The fixing region 436 isarranged to overlap with at least a portion of the lower radial dynamicpressure bearing portion 812 in the radial direction. As a result, bothan increase in the axial length of the radial gap 62 and an increase inthe axial dimension of the fixing region 436 are achieved. Moreover, anarea surrounding a lower portion of the radial dynamic pressure bearing81 is surrounded by the base plate 21. This results in increasedrigidity of the surroundings of the lower portion of the radial dynamicpressure bearing 81. Moreover, a reduction in the thickness of the motor12 as a whole in a direction parallel or substantially parallel to thecentral axis J1 is achieved.

Because the shaft portion 41 and the upper thrust portion 42 arepreferably defined by a single continuous monolithic member, and becausethe lower plate portion 431 and the outer tubular portion 432 arepreferably defined by a single continuous monolithic member, a reductionin the number of components of the motor 12 and a reduction in thenumber of steps required to assemble the motor 12 are achieved. It iseasy to define the communicating hole 61 in the sleeve portion 5 becausethe communicating hole 61 is arranged to have a small axial length andto extend in parallel or substantially in parallel with the central axisJ1. A reduction in the total amount of the lubricating oil 45 is alsoachieved. Note that the diameter of the communicating hole 61 may bereduced to as small as the width of the cylindrical gap 64 to achieve anadditional reduction in the amount of the lubricating oil 45.

FIG. 9 is a bottom view of the inner tubular portion 51. Referring toFIG. 9, in the motor 12, a lower surface of the inner tubular portion 51may include a thrust dynamic pressure groove array 723 defined therein.A thrust dynamic pressure bearing portion arranged to support the innertubular portion 51 in the thrust direction is thereby defined in thelower end gap 63 illustrated in FIG. 3. In this case, a dynamic pressuregeneration portion that functions as a thrust dynamic pressure bearingportion may not necessarily be arranged in the lower thrust gap 652.Note, however, that it is preferable that a dynamic pressure groovearray which defines a dynamic pressure generation portion arranged toinduce a radially inward pressure acting on the lubricating oil 45should be arranged in the lower thrust gap. In the case of the structureillustrated in FIG. 9, the axial width of the lower thrust gap ispreferably arranged to be greater than that of the lower end gap. Thesame holds true for a second preferred embodiment of the presentinvention described below.

Second Preferred Embodiment

FIG. 10 is a diagram illustrating a portion of a bearing mechanism 4 ain a motor according to the second preferred embodiment of the presentinvention. A sleeve portion 5 a of the bearing mechanism 4 a includes anupper inner tubular portion 55. The upper inner tubular portion 55 isannular and arranged to extend axially upward from a radially innerportion of the flange portion 52. Hereinafter, the inner tubular portion51, which is arranged below the flange portion 52, will be referred toas a “lower inner tubular portion 51” when the inner tubular portion 51is distinguished from the upper inner tubular portion 55. An upperthrust portion 42 a includes an upper plate portion 424 and an upperouter tubular portion 425. The upper plate portion 424 is arranged toextend radially outward from the upper portion of the shaft portion 41.The upper outer tubular portion 425 is arranged to extend downward froman outer edge portion of the upper plate portion 424. Hereinafter, theplate portion 431 of the lower thrust portion 43 will be referred to asa “lower plate portion 431” when the plate portion 431 is distinguishedfrom the upper plate portion 424. The outer tubular portion 432 will bereferred to as a “lower outer tubular portion 432” when the outertubular portion 432 is distinguished from the upper outer tubularportion 425. The bearing mechanism 4 a is otherwise similar in structureto the bearing mechanism 4 in the motor 12 according to the firstpreferred embodiment of the present invention. Note that like members orportions are designated by like reference numerals in the followingdescription.

The upper thrust portion 42 a includes the shoulder portion 423 recessedaxially downward and defined between an upper surface of the upper plateportion 424 and an outer circumferential surface 429 of the upper outertubular portion 425. While some of the reference symbols shown in FIG. 8are omitted in FIG. 10, the radially extending gap 663 a is definedbetween the outer annular surface 742 of the shoulder portion 423 andthe lower surface of the cap cover portion 442 as in FIG. 8. Inaddition, the axially extending gap 663 b is defined between the innercylindrical surface 741 and the inner edge 443 of the cap cover portion442. Thus, as in the first preferred embodiment, a reduction in theevaporation of the lubricating oil 45 through the upper seal portion 661a, and an improvement in the life of the motor are achieved.

Referring to FIG. 10, a gap 671 is defined between an upper surface 551of the upper inner tubular portion 55 and a lower surface 426 of theupper plate portion 424 in the axial direction, i.e., in the verticaldirection in FIG. 10. Hereinafter, the gap 671 will be referred to as an“upper end gap 671”. In addition, a cylindrical gap 672 is definedbetween an outer circumferential surface 552 of the upper inner tubularportion 55 and an inner circumferential surface 427 of the upper outertubular portion 425 in the radial direction. Hereinafter, the gap 672will be referred to as an “upper cylindrical gap 672”. Hereinafter, thecylindrical gap 64, which is defined between the outer circumferentialsurface 512 of the lower inner tubular portion 51 and the innercircumferential surface 434 of the lower outer tubular portion 432, willbe referred to as a “lower cylindrical gap 64” when the cylindrical gap64 is distinguished from the upper cylindrical gap 672.

An upper thrust dynamic pressure groove array 721 similar to thatillustrated in FIG. 6 is defined in a lower surface 428 of the upperouter tubular portion 425 of the upper thrust portion 42 a. As a result,the upper thrust dynamic pressure bearing portion 821 is defined in theupper thrust gap 651 between the lower surface 428 of the upper outertubular portion 425 and the upper surface 521 of the flange portion 52.In the bearing mechanism 4 a, the upper thrust dynamic pressure bearingportion 821 and the radial dynamic pressure bearing 81 are arranged incommunication with each other through the upper cylindrical gap 672 andthe upper end gap 671.

The upper seal portion 661 a is defined between the outercircumferential surface 429 of the upper outer tubular portion 425 andthe inner circumferential surface 531 of the upper hub tubular portion53. The lower seal portion 662 a is defined between the inclined surface433 of the lower outer tubular portion 432 and the inner circumferentialsurface 541 of the lower hub tubular portion 54. The upper seal portion661 a and the lower seal portion 662 a are arranged in communicationwith each other through the communicating hole 61. The axial distancebetween the upper end of the surface of the lubricating oil 45 in theupper seal portion 661 a and the lower end of the surface of thelubricating oil 45 in the lower seal portion 662 a is preferably longerthan the length of the communicating hole and shorter than the length ofthe radial dynamic pressure bearing 81.

Also in the second preferred embodiment of the present invention, theaxial distance between the surface of the lubricating oil 45 in theupper seal portion 661 a and the surface of the lubricating oil 45 inthe lower seal portion 662 a is shorter than the length of the radialdynamic pressure bearing 81. This arrangement contributes to reducingthe difference in pressure between the upper and lower seal portions 661a and 662 a. This contributes to preventing a leakage of the lubricatingoil 45. Furthermore, the length of the communicating hole 61 beingshorter than the distance between the upper seal portion 661 a and thelower seal portion 662 a makes it easier to prevent any leakage of thelubricating oil 45.

Providing the upper cylindrical gap 672 and the lower cylindrical gap 64contributes to reducing the length of the communicating hole 61. Thereduced length of the communicating hole 61 contributes to arranging theupper seal portion 661 a and the lower seal portion 662 a to be closerto each other, whereby a leakage of the lubricating oil 45 is moreeasily prevented. Moreover, the upper end gap 671 and the uppercylindrical gap 672 are arranged between the upper thrust dynamicpressure bearing portion 821 and the radial dynamic pressure bearing 81.This arrangement contributes to increased pressure on the lubricatingoil 45 in the upper end gap 671 and the upper cylindrical gap 672,whereby generation of an air bubble is prevented therein.

In the bearing mechanism 4 a, the upper surface 551 of the upper innertubular portion 55 may include a thrust dynamic pressure groove arraysimilar to the thrust dynamic pressure groove array 723 illustrated inFIG. 9 defined therein. This results in a thrust dynamic pressurebearing portion being defined in the upper end gap 671 to support theupper inner tubular portion 55 in the thrust direction. In this case, adynamic pressure generation portion that functions as an upper thrustdynamic pressure bearing portion may not necessarily be arranged in theupper thrust gap 651. Note, however, that it is preferable that adynamic pressure groove array which defines a dynamic pressuregeneration portion arranged to produce a radially inward pressure actingon the lubricating oil 45 should be arranged in the upper thrust gap651. The axial width of the upper end gap 671 is preferably greater thanthat of the upper thrust gap 651.

Third Preferred Embodiment

FIG. 11 is a diagram illustrates a motor 12 a according to a thirdpreferred embodiment of the present invention. In the motor 12 a, thesleeve portion 5, an upper hub tubular portion 53 a, and the lower hubtubular portion 54 are preferably defined by a single continuousmonolithic member. In addition, the cover portion 311 and thecylindrical portion 312 are preferably defined by a single continuousmonolithic member. The upper hub tubular portion 53 a includes anannular projecting portion 532 arranged to project upward. A seal cap 44a is arranged to be annular and centered on the central axis J1. In themotor 12 a, the upper hub tubular portion 53 a defines the tubularportion of the upper hub annular portion 591. In addition, the seal cap44 a defines the annular cover portion of the upper hub annular portion591. The motor 12 a is otherwise substantially similar in structure tothe motor 12 according to the first preferred embodiment of the presentinvention.

Referring to FIG. 12, in the motor 12 a, a radially outer edge 444 ofthe seal cap 44 a is tightly fitted to an inner circumferential surfaceof the projecting portion 532. Note that the outer edge 444 may be fixedto the upper hub tubular portion 53 a preferably through, for example,an adhesive. Also note that the outer edge 444 may be fixed to the upperhub tubular portion 53 a through, for example, a combination of thetight fit and use of the adhesive, if so desired.

FIG. 13 is a cross-sectional view of the seal cap 44 a. FIG. 14 is abottom view of the seal cap 44 a. The inner edge 443 of the seal cap 44a preferably includes an inner annular projecting portion 461 arrangedto project downward. A lower surface of the seal cap 44 a includes arecessed portion 462 recessed upward. The depth of the recessed portion462 is preferably arranged in the range of about 10 μm to about 50 μm,for example. Referring to FIG. 12, the upper thrust portion 42 includesa groove portion 744 having a great depth and defined between the innercylindrical surface 741, which is arranged radially inward of the outercircumferential surface 422, and the outer annular surface 742, which isarranged radially outward of the inner cylindrical surface 741. Theupper end of the inner cylindrical surface 741 is arranged at an axiallevel higher than that of the upper end of the outer circumferentialsurface 422 and that of the outer annular surface 742.

A lower end of the inner annular projecting portion 461 of the seal cap44 a is arranged inside the groove portion 744. The radially extendinggap 663 a, which is annular and arranged to extend perpendicularly orsubstantially perpendicularly to the central axis J1, is defined betweena bottom surface 445 of the recessed portion 462, which is perpendicularor substantially perpendicular to the central axis J1, and the outerannular surface 742 of the upper thrust portion 42.

The axial width of the radially extending gap 663 a is arranged to besmaller than the maximum radial width of the upper seal gap 661. Inother words, the axial width of the radially extending gap 663 a isarranged to be smaller than the radial distance between an upper edge ofa chamfer 661 b defined between the outer annular surface 742 and theouter circumferential surface 422 and an upper edge of a chamfer 661 cdefined at an inner top portion of the upper hub tubular portion 53 a.Note that, in the case where the upper thrust portion 42 and the upperhub tubular portion 53 a are not provided with the chamfers 661 b and661 c, respectively, in the upper portion of the upper seal gap 661, themaximum radial width of the upper seal gap 661 refers to the radialdistance between an upper edge of the outer circumferential surface 422and an upper edge of the inner circumferential surface 531 of the upperhub tubular portion 53 a.

The axial width of the radially extending gap 663 a is preferablyarranged in the range of about 0.05 mm to about 0.2 mm, for example. Theradially extending gap 663 a is continuous with the upper portion of theupper seal gap 661. Each of the outer annular surface 742 and the bottomsurface 445 of the recessed portion 462 is coated with an oil-repellentagent about its entire circumference. Hereinafter, an annular regionthat surrounds the central axis J1 and which is coated with anoil-repellent film 86 on the bottom surface 445 of the recessed portion462 of the seal cap 44 a will be referred to as a “first oil-repellentfilm region 851”. An annular region that surrounds the central axis J1and which is coated with an oil-repellent film 86 on the outer annularsurface 742 will be referred to as a “second oil-repellent film region852”.

A strong physical shock to the motor 12 a may cause droplets of thelubricating oil 45 in the upper seal gap 661 to be scattered, so thatsome of the droplets may be adhered to the lower surface of the seal cap44 a or the outer annular surface 742. Provision of the first and secondoil-repellent film regions 851 and 852 in the motor 12 a contributes toprevention of the droplets of the lubricating oil 45 from travelingradially inward on the lower surface of the seal cap 44 a or the outerannular surface 742. The lubricating oil 45 is thus prevented fromtraveling through the radially extending gap 663 a to be leaked out ofthe motor 12 a. In other words, the lubricating oil 45 is prevented fromtraveling radially inward beyond the first and second oil-repellent filmregions 851 and 852. Moreover, the provision of the first oil-repellentfilm region 851 and the second oil-repellent film region 852 contributesto more effective prevention of a leakage of the lubricating oil 45 outof the upper seal gap 661. Furthermore, because the radially extendinggap 663 a is a minute gap, the provision of at least one of the firstoil-repellent film region 851 and the second oil-repellent film region852 reduces the leakage of the lubricating oil 45 out of the upper sealgap 661.

Referring to FIGS. 13 and 14, the lower surface of the seal cap 44 aincludes shoulder portions 462 a and 462 b. The shoulder portion 462 ais annular and arranged to extend radially inward from the bottomsurface 445 while extending downward. The shoulder portion 462 b isannular and arranged to extend radially outward from the bottom surface445 while extending downward. As illustrated in FIG. 12, the shoulderportion 462 a, which is arranged radially inward of the bottom surface445, is arranged radially inward of the radially extending gap 663 a. Itis possible to use the shoulder portions 462 a and 462 b illustrated inFIGS. 13 and 14 as marks to properly apply the oil-repellent agent ontothe bottom surface 445 of the seal cap 44 a. Note that, if so desired,the oil-repellent agent may be applied to the shoulder portions 462 aand 462 b as well.

As illustrated in FIG. 12, the axially extending gap 663 b, which isarranged to open into the space above the upper thrust portion 42, isdefined between the inner annular projecting portion 461 and the innercylindrical surface 741. The radial width of the axially extending gap663 b is preferably arranged in the range of about 0.05 mm to about 0.2mm, for example. The radially extending gap 663 a is arranged incommunication with the axially extending gap 663 b through the grooveportion gap 663 c, which is defined between the groove portion 744 andthe seal cap 44 a. In the motor 12 a, the communicating gap 663, whichis arranged to communicate the upper seal gap 661 with the space abovethe upper thrust portion 42, is defined by the radially extending gap663 a, the groove portion gap 663 c, and the axially extending gap 663b.

Also in the third preferred embodiment of the present invention, theinclusion of the radially extending gap 663 a and the axially extendinggap 663 b in the communicating gap 663 contributes to preventing an aircontaining an evaporated lubricating oil in the upper seal gap 661 fromtraveling to the outside of the motor 12 a. This contributes to reducingthe evaporation of the lubricating oil 45, and thereby achieving animprovement in a usable life of the motor 12 a. Moreover, because thelower end of the inner annular projecting portion 461 is arranged insidethe groove portion 744, a further reduction in the evaporation of thelubricating oil 45 is achieved. The same holds true for similarstructures in other preferred embodiments described below.

The provision of the groove portion 744 in the upper thrust portion 42makes it possible to arrange the inner annular projecting portion 461 inclose proximity to the inner cylindrical surface 741. Thus, the axiallyextending gap 663 b can be easily defined. The provision of the innerannular projecting portion 461 in the seal cap 44 a contributes to anincreased axial dimension of the axially extending gap 663 b, and alsoto an increased rigidity of the seal cap 44 a. In particular, becauseflexural strength of the seal cap 44 a is thereby improved, the seal cap44 a is prevented from undergoing a deformation when the seal cap 44 ais, for example, press fitted to be thereby fixed to the projectingportion 532. The motor 12 a is able to achieve a reduction in the axialthickness of the seal cap 44 a, and a reduction in the total size of themotor 12 a. Regarding a storage disk drive including the motor 12 a,when the upper plate member 142 of the housing 14 as illustrated in FIG.1 is fixed to the motor 12 a, a strong force may be applied to the upperthrust portion 42. Even if that happens, the force is absorbed bybending of the inner cylindrical surface 741 and the groove portion 744,and the lower surface 421 of the upper thrust portion 42 is preventedfrom undergoing a substantial deformation. As a result, a reduction inperformance of the upper thrust dynamic pressure bearing portion 821 issubstantially prevented.

FIG. 15 is a diagram illustrating a portion of a motor 12 a according toanother preferred embodiment of the present invention. The radiallyouter edge 444 of the seal cap 44 a of the motor 12 a includes an outerannular projecting portion 463 arranged to project upward. An outercircumferential surface of the outer annular projecting portion 463 istightly fitted and thereby fixed to the projecting portion 532. Theinclusion of the outer annular projecting portion 463 in the seal cap 44a contributes to an increase in an area where the seal cap 44 a is indirect contact with the projecting portion 532. The increase in thecontact area contributes to an improvement in strength with which theseal cap 44 a is, for example, press fitted to the projecting portion532. Note that, in the case where the outer annular projecting portion463 and the projecting portion 532 are fixed to each other through, forexample, an adhesive, an improvement in adhesive strength therebetweenis achieved.

FIG. 16 is a diagram illustrating a motor 12 a according to yet anotherpreferred embodiment of the present invention. The projecting portion532 of the upper hub tubular portion 53 a includes a raised portion 533that is raised radially inward. In the motor 12 a, an upper edge of theouter edge 444 of seal cap 44 a and the raised portion 533 are arrangedin contact with each other in the axial direction. This contributes tomore effectively preventing the seal cap 44 a from coming off the upperhub tubular portion 53 a. When the seal cap 44 a is fixed to the upperhub tubular portion 53 a, the outer edge 444 of the seal cap 44 a ismoved downward while undergoing an upward elastic deformation when beingin contact with the raised portion 533, and once the outer edge 444 ismoved downward beyond the raised portion 533, the outer edge 444 regainsits original shape thanks to resilience.

FIG. 17 is a diagram illustrating the upper seal gap 661 and itsvicinity of a motor according to yet another preferred embodiment of thepresent invention. An upper portion 530 of the upper hub tubular portion53 a includes a shoulder portion 534. The shoulder portion 534 isarranged in a region that is radially inward of the projecting portion532 and which is axially opposed to the seal cap 44 a, and is arrangedto extend radially outward while extending upward. In the upper portion530 of the upper hub tubular portion 53 a, the shoulder portion 534, aninner annular surface 535, which is annular and centered on the centralaxis J1 and which is arranged radially inward of the shoulder portion534, and the chamfer 661 c are coated with an oil-repellent film 86throughout their entire circumference. Hereinafter, the shoulder portion534, the inner annular surface 535, and the chamfer 661 c will becollectively referred to as a “third oil-repellent film region 853”. Inaddition, as in the case of FIG. 12, the lower surface of the seal cap44 a and the outer annular surface 742 of the upper thrust portion 42are provided with the first and second oil-repellent film regions 851and 852, respectively.

Providing the third oil-repellent film region 853, which is annular andarranged to surround the central axis J1, in the upper portion 530 ofthe upper hub tubular portion 53 a contributes to preventing a leakageof the lubricating oil 45 due to a centrifugal force when the rotationof the motor 12 is examined before the attachment of the seal cap 44 a.It is possible to use the shoulder portion 534 as a mark to properlyapply the oil-repellent agent onto the inner annular surface 535 and thechamfer 661 c of the upper hub tubular portion 53 a.

Moreover, when the lubricating oil 45 is injected into the bearingmechanism 4 through the lower seal gap 662 illustrated in FIG. 4 withthe bearing mechanism 4 turned upside down, the provision of the secondand third oil-repellent film regions 852 and 853 contributes topreventing a portion of the lubricating oil 45 which has flowed into theupper seal gap 661 from traveling beyond the outer annular surface 742of the upper thrust portion 42 or the upper portion 530 of the upper hubtubular portion 53 a.

Note that, in the bearing mechanism 4, the position of the thirdoil-repellent film region 853 may be modified appropriately as long asat least a portion of the third oil-repellent film region 853 isarranged radially inward of the shoulder portion 534. For example, anupper portion of the inner circumferential surface 531 may define aportion of the third oil-repellent film region. Also note that theoil-repellent film 86 may not necessarily be arranged to extend over theshoulder portion 534, but the third oil-repellent film region may bearranged to extend over only the inner annular surface 535, the chamfer661 c, and the upper portion of the inner circumferential surface 531.Also note that the third oil-repellent film region may be arranged toextend over only the inner annular surface 535, and that the thirdoil-repellent film region may be arranged to extend over only thechamfer 661 c.

Fourth Preferred Embodiment

FIG. 18 is a diagram illustrating a portion of a storage disk drive 1including a motor according to a fourth preferred embodiment of thepresent invention. The structure of this motor is similar to that of themotor 12 a illustrated in FIG. 11. An upper surface 440 of the seal cap44 a according to the present preferred embodiment includes a surface440 a that is arranged at an axial level higher than that of asurrounding area and which is arranged axially opposite an outer edgeportion of a lower surface 143 a of the plate central portion 143 of thehousing. Note that the upper surface 440 refers to a surface whosenormal is pointed axially upward. In the storage disk drive 1, anannular, radially extending gap 663 d is defined between the surface 440a and the lower surface 143 a of the plate central portion 143.Hereinafter, the radially extending gap 663 a, which is defined betweenthe seal cap 44 a and the upper thrust portion 42 will be referred to asa “first radially extending gap 663 a”, while the gap 663 d will bereferred to as a “second radially extending gap 663 d”. The axial widthof the second radially extending gap 663 d is preferably arranged in therange of about 0.05 mm to about 0.2 mm, for example. The second radiallyextending gap 663 d is arranged in communication with the axiallyextending gap 663 b through a gap 663 e defined between the lowersurface 143 a of the plate central portion 143 and a radially innerportion of the upper surface 440 of the seal cap 44 a. Note that theaxial width of the gap 663 e is also preferably arranged in the range ofabout 0.05 mm to about 0.2 mm, for example.

In the storage disk drive 1, a communicating gap 664 arranged to bringthe upper seal gap 661 into communication with the space outside themotor includes the first radially extending gap 663 a, the grooveportion gap 663 c, the axially extending gap 663 b, the gap 663 e, andthe second radially extending gap 663 d. As is the case with the firstradially extending gap 663 a and the axially extending gap 663 b, thesecond radially extending gap 663 d is a region that has a locallydecreased width within the communicating gap 664 and which has a widthsmaller than the maximum radial width of the upper seal gap 661.

Also in the fourth preferred embodiment, a reduction in the evaporationof the lubricating oil 45 is achieved because the communicating gap 664is arranged to have a labyrinth structure, including radially extendinggaps and an axially extending gap. The provision of the second radiallyextending gap 663 d, which has a decreased axial width, contributes toan additional reduction in the evaporation of the lubricating oil 45.

While preferred embodiments of the present invention have been describedabove, the present invention is not limited to the above-describedpreferred embodiments, but a variety of modifications are possible. Forexample, referring to FIG. 19, in a modification of the third preferredembodiment, the lower surface of the seal cap 44 a may include anannular raised portion 464 arranged to project downward. In this case,an oil-repellent agent is applied onto a surface 464 a of the raisedportion 464 which is perpendicular to the central axis J1. The seal cap44 a includes an annular shoulder portion 464 b arranged to extendradially inward from the surface 464 a while extending upward, and anannular shoulder portion 464 c arranged to extend radially outward fromthe surface 464 a while extending upward. It is possible to use theshoulder portions 464 b and 464 c as marks for proper application of theoil-repellent agent.

The region where the oil-repellent agent is to be applied is made easilyidentifiable by arranging a portion of the lower surface of the seal cap44 a which is radially inward of the radially extending gap 663 a at alevel higher or lower than that of a portion of the lower surface of theseal cap 44 a which defines the radially extending gap 663 a.Furthermore, referring to FIG. 20, the lower surface of the seal cap 44a may include a minute recessed portion 465 defined by an annular cut.The minute recessed portion 465 is arranged radially inward of theradially extending gap 663 a illustrated in FIG. 12. The oil-repellentagent is applied onto a portion of the lower surface of the seal cap 44a which is radially outward of the minute recessed portion 465.Alternatively, the lower surface of the seal cap 44 a may include anannular, minute raised portion.

As described above, the provision of an annular shoulder portionextending upward or downward while extending radially inward in at leasta portion of the lower surface of the seal cap 44 a which is radiallyinward of the radially extending gap 663 a makes it easier to properlyapply the oil-repellent agent onto a portion of the lower surface of theseal cap 44 a which is radially outward of the shoulder portion. Thesame holds true for the first radially extending gap 663 a illustratedin FIG. 18. Regarding the upper hub tubular portion 53 a illustrated inFIG. 12, the third oil-repellent film region 853 may be arranged in thechamfer 661 c, which is arranged in the vicinity of an upper end openingof the upper seal gap 661, and an area surrounding the chamfer 661 c,unless the oil-repellent film 86 applied thereto affects the attachmentof the seal cap 44 a. In each of the first, second, and fourth preferredembodiments, as well as in the third preferred embodiment, the first andsecond oil-repellent film regions may be arranged in the lower surfaceof the seal cap 44 or 44 a and the outer annular surface 742 of theupper thrust portion 42 or 42 a, respectively. The third oil-repellentfilm region may be arranged in the upper portion of the upper hubtubular portion 53 or 53 a.

Referring to FIG. 21, in a modification of the third preferredembodiment, an inner annular projecting portion 466 projecting upwardmay be arranged at the inner edge 443 of the seal cap 44 a such that theaxially extending gap 663 b is defined between the inner annularprojecting portion 466 and the inner cylindrical surface 741. The inneredge 443 including an annular projecting portion arranged to project inthe axial direction makes it easier to secure a sufficient length of theaxially extending gap 663 b while securing a sufficient rigidity of theseal cap 44 a.

Referring to FIG. 22, the inner edge 443 of the seal cap 44 a may bearranged to extend perpendicularly or substantially perpendicularly tothe central axis J1. Even in this case, it is possible to define aradially extending gap having a large radial dimension below the sealcap 44 a, and thereby reduce the evaporation of the lubricating oil 45.Referring to FIG. 23, in a modification of the first preferredembodiment, the upper thrust portion 42 and the shaft portion 41 may bedefined by separate members. In this case, the shaft portion 41 isinserted into the upper thrust portion 42 from below, and a portion 471of the upper thrust portion 42 which is defined in the upper portionthereof and which is arranged to project radially inward is arranged inaxial contact with an upper end of the shaft portion 41. Axialpositioning of the upper thrust portion 42 relative to the shaft portion41 is thereby achieved. The provision of the portion 471 contributes tosecurely preventing a downward movement of the upper thrust portion 42.Also, referring to FIG. 24, the outer circumferential surface 411 of theshaft portion 41 may include a shoulder portion 472. In this case, aradially inner end portion of a bottom portion of the upper thrustportion 42 can be arranged in axial contact with the shoulder portion472 to achieve the axial positioning of the upper thrust portion 42relative to the shaft portion 41. The same holds true for otherpreferred embodiments.

The seal cap 44 or 44 a may be welded to the upper hub tubular portion53 or 53 a, for example. The lower thrust portion 43 and the base plate21 may be defined by a single continuous member, for example. In thiscase, a reduction in the number of components of the motor is achieved.Also, in each of the first and second preferred embodiments, the shaftportion 41 and the upper thrust portion 42 may be defined by separatemembers. Also, the lower plate portion 431 and the outer tubular portion432 may be defined by separate members. Also, the lower thrust portion43 and the shaft portion 41 may be defined by a single continuousmember.

In the groove upper portion of the upper radial dynamic pressure groovearray 711 illustrated in FIG. 5, a plurality of oblique grooves may bearranged to extend obliquely along the grooves constituting the upperradial dynamic pressure groove array 711. Also, in the groove upperportion, each of the grooves constituting the upper radial dynamicpressure groove array 711 may be arranged to have a greater depth thanin the groove lower portion. This leads to an increased axially downwardpressure acting on the lubricating oil 45. The same holds true for thegroove lower portion of the lower radial dynamic pressure groove array712. Also, the upper portion and the lower portion of each of thegrooves that define the upper radial dynamic pressure groove array 711may be arranged to have substantially the same length. Also, the upperportion and the lower portion of each of the grooves that constitute thelower radial dynamic pressure groove array 712 may be arranged to havesubstantially the same length. A variety of modifications can be made tothe length, depth, width, and so on of each of the dynamic pressuregrooves without departing from the scope and spirit of the presentinvention.

Each of the upper thrust dynamic pressure groove array 721 and the lowerthrust dynamic pressure groove array 722 may be arranged in theherringbone pattern. In this case, a radially outer portion of each ofupper thrust dynamic pressure grooves that define the upper thrustdynamic pressure groove array 721 is arranged to have a length greaterthan that of a radially inner portion thereof, and a radially outerportion of each of lower thrust dynamic pressure grooves that define thelower thrust dynamic pressure groove array 722 is arranged to have alength greater than that of a radially inner portion thereof, in orderto generate a radially inward pressure acting on the lubricating oil 45.Note that a plurality of oblique grooves may be arranged between theradially outer portions of the thrust dynamic pressure grooves. Theradially outer portion of each thrust dynamic pressure groove may bearranged to have a depth greater than that of the radially inner portionthereof. Although a direction in which the lubricating oil 45 circulateshas not been specified in the description of any of the above-describedpreferred embodiments, the direction in which the lubricating oil 45circulates may be determined to be either a counterclockwise directionor a clockwise direction in FIG. 4.

In FIG. 4, in the case where the lower surface 421 of the upper thrustportion 42 is arranged to have a sufficient area, the upper thrustdynamic pressure groove array 721 may be arranged radially inward of theupper end opening of the communicating hole 61 as illustrated in FIG.25. Furthermore, the upper thrust dynamic pressure groove array 721 maybe arranged farther radially inward of the communicating hole 61 than inthe case of FIG. 25. Similarly, in the case where the upper surface 435of the outer tubular portion 432 is arranged to have a sufficient area,the lower thrust dynamic pressure groove array 722 may be arrangedradially inward of the lower end opening of the communicating hole 61 asillustrated in FIG. 26. Furthermore, the lower thrust dynamic pressuregroove array 722 may be arranged farther radially inward of thecommunicating hole 61 than in the case of FIG. 26. In the upper andlower thrust gaps 651 and 652, an upper thrust dynamic pressure groovearray and a lower thrust dynamic pressure groove array may be arrangedin the upper surface 521 and the lower surface 522, respectively, of theflange portion 52. Also, a radial dynamic pressure groove array may bearranged in the outer circumferential surface 411 of the shaft portion41.

In each of the above-described preferred embodiments, the upper seal gap661 may be arranged to have a substantially uniform width. In that case,a dynamic pressure groove array is arranged in at least one of the outercircumferential surface 422 of the upper thrust portion 42 and the innercircumferential surface 531 of the upper hub tubular portion 53 todefine a so-called pumping seal. A dynamic pressure acting on thelubricating oil 45 in the direction of an interior of the upper seal gap661 is thereby generated to retain the lubricating oil 45. The sameholds true for the lower seal gap 662. Each of the upper seal portion661 a and the lower seal portion 662 a may not necessarily be arrangedto extend in parallel or substantially in parallel with the central axisJ1, but may be arranged to be angled significantly with respect to thecentral axis J1.

Referring to FIG. 27, the cap cylindrical portion 441 of the seal cap 44may be fixed to an inside of the upper hub tubular portion 53. In thiscase, an inner circumferential surface of the tubular portion of theupper hub annular portion 591 is defined by an inner circumferentialsurface of the cap cylindrical portion 441, and the upper seal gap 661is defined between the inner circumferential surface of the capcylindrical portion 441 and the outer circumferential surface 422 of theupper thrust portion 42. The cap cylindrical portion 441 may be regardedas a portion of the upper hub tubular portion 53. It is, however, morepreferable that at least the inner circumferential surface of thetubular portion of the upper hub annular portion 591 is defined by theinner circumferential surface of the upper hub tubular portion 53 or 53a so that the volume of the lubricating oil 45 in the upper seal gap 661can be checked and verified before the attachment of the seal cap 44. Inthe upper hub annular portion 591, the upper hub tubular portion and theseal cap may be defined by a single continuous member, for example.Also, in the case where the likelihood of a leakage of the lubricatingoil 45 is low, the seal cap 44 or 44 a may be eliminated with the upperhub annular portion being defined by only the upper hub tubular portion53 or 53 a.

FIG. 28 is a cross-sectional view illustrating an upper thrust portion42 a, a tubular portion 54, an annular cover portion, and theirvicinities according to a preferred embodiment of the present invention.The structure of a motor 12 a according to the present preferredembodiment is preferably identical or substantially identical to that ofthe motor 12 a illustrated in FIG. 11.

The upper thrust portion 42 a preferably includes a first outercircumferential surface 4221, a second outer circumferential surface4222, and a third outer circumferential surface 4223. Each of the firstand second outer circumferential surfaces 4221 and 4222 is tubular inshape. The third outer circumferential surface 4223 is annular in shape.The first outer circumferential surface 4221 is arranged radiallyoutside the upper thrust portion 42 a. The third outer circumferentialsurface 4223 is arranged to extend radially inward and axially upwardfrom an upper end of the first outer circumferential surface 4221. Thesecond outer circumferential surface 4222 is arranged to extend axiallyupward from an upper end of the third outer circumferential surface.That is, both the second and third outer circumferential surfaces 4222and 4223 are arranged radially inward of and axially above the firstouter circumferential surface 4221, and the first and second outercircumferential surfaces 4221 and 4222 are joined to each other by thethird outer circumferential surface 4223.

The first outer circumferential surface 4221 and an innercircumferential surface of the tubular portion 54 are arranged totogether define an upper seal gap 661 therebetween. The first outercircumferential surface 4221 is an inclined surface arranged toobliquely extend radially inward and axially upward. The innercircumferential surface of the tubular portion 54 is either an inclinedsurface arranged to extend parallel or substantially parallel to thecentral axis, or an inclined surface having a smaller angle ofinclination than that of the first outer circumferential surface 4221.Accordingly, the radial distance between the first outer circumferentialsurface 4221 and the inner circumferential surface of the tubularportion 54, that is, the width of the upper seal gap 661, increases withincreasing height. In addition, a surface of a lubricating oil 45 islocated between the first outer circumferential surface 4221 and theinner circumferential surface of the tubular portion 54.

Because of the above arrangement, the surface of the lubricating oil 45is attracted downward through capillary action. This contributes topreventing the surface of the lubricating oil 45 from moving upward inthe upper seal gap 661 due to an increase in the volume of thelubricating oil 45 caused by a centrifugal force, a rise in atemperature, or the like, for example, or due to some other action.

The annular cover portion preferably includes a plate portion 467arranged to extend radially, an inner annular projecting portion 461arranged to project axially from a radially inner end portion of theplate portion 467, and an annular inclined portion 468. The innerannular projecting portion 461 is arranged to project downward in thepresent preferred embodiment. In addition, an inner circumferentialsurface of the inner annular projecting portion 461 is arranged abovethe inner circumferential surface of the tubular portion 54. Note that,although the inner annular projecting portion 461 preferably is arrangedto project downward in the present preferred embodiment, the presentinvention is not limited to the present preferred embodiment. Forexample, the inner annular projecting portion 461 may be arranged toproject upward instead of downward. In addition, the annular coverportion preferably includes the annular inclined portion 468, which isarranged to obliquely extend radially outward and axially downward. Thismakes it possible to arrange a surface of an adhesive 90 between aprojecting portion 532 and an outer edge portion of the annular coverportion including the inclined portion 468 above an upper surface of theannular cover portion. As a result, a gap between an outercircumferential surface of the annular cover portion and an innercircumferential surface of the projecting portion 532 is sealed with theadhesive 90, so that a leakage of the lubricating oil 45 through the gapis prevented. Moreover, the adhesive 90 is preferably prevented frombeing located higher than the projecting portion 532 or the plateportion 467.

An upper end of the second outer circumferential surface 4222 isarranged at an axial height higher than that of an upper end of theinner annular projecting portion 461. The third outer circumferentialsurface 4223 is arranged to have a radial width smaller than the axialwidth of the second outer circumferential surface 4222. In addition, thethird outer circumferential surface 4223 is an annular inclined surfacearranged to extend radially outward and axially downward. Moreover, thethird outer circumferential surface 4223 is arranged to axially overlapwith a lower surface of the inner annular projecting portion 461.

Note that an annular groove portion which is recessed downward may belocated between the second and third outer circumferential surfaces 4222and 4223.

An axially extending gap 663 d is preferably provided between the innercircumferential surface of the inner annular projecting portion 461 andthe second outer circumferential surface 4222. The axially extending gap663 d extends in the axial direction. The axially extending gap 663 d isarranged to have a radial width smaller than a maximum width of theupper seal gap 661. In addition, the radial distance between an innercircumferential surface of the annular cover portion and the secondouter circumferential surface 4222 is arranged to be shorter than theaxial distance between a lower surface of the annular cover portion andthe third outer circumferential surface 4223. The arrangement of theaxially extending gap 663 d contributes to reducing evaporation of thelubricating oil 45. Moreover, the axial extension of the inner annularprojecting portion 461 contributes to lengthening the axially extendinggap 663 d. This leads to an additional reduction in the evaporation ofthe lubricating oil 45, leading to an improvement in a life of the motor12 a.

An upper surface of the tubular portion 54 preferably includes anannular first oil-repellent film portion 853 on which an oil-repellentfilm is arranged. In addition, the upper surface of the tubular portion54 includes a contact surface 541 arranged to be in axial contact withthe lower surface of the annular cover portion. At least a portion ofthe first oil-repellent film portion 853 is arranged radially inward ofthe contact surface 541. This contributes to preventing the surface ofthe lubricating oil 45 from moving radially outward beyond the tubularportion 54 due to the centrifugal force during rotation of the motor 12a.

The second and third outer circumferential surfaces 4222 and 4223preferably include an annular second oil-repellent film portion 854 onwhich an oil-repellent film 86 is arranged. It is enough that the secondoil-repellent film portion 854 should be arranged in at least one of thesecond and third outer circumferential surfaces 4222 and 4223.Therefore, the position of the second oil-repellent film portion 854 maybe changed appropriately. For example, a portion of the secondoil-repellent film portion 854 may be arranged in a top portion of thefirst outer circumferential surface 4221. Also note that the entiresecond oil-repellent film portion 854 may be arranged in the secondouter circumferential surface 4222 with no portion of the oil-repellentfilm 86 being arranged on the third outer circumferential surface 4223.Also note that the entire second oil-repellent film portion 854 may bearranged in the third outer circumferential surface 4223.

The inner circumferential surface of the inner annular projectingportion 461 includes an annular third oil-repellent film portion 855 onwhich an oil-repellent film 86 is arranged. The third oil-repellent filmportion 855 is arranged both axially and radially opposite to the secondoil-repellent film portion 854. This arrangement contributes topreventing the lubricating oil 45 from leaking out of the motor throughthe axially extending gap 663 d even when the motor is driven with abearing mechanism 4 turned upside down. Each oil-repellent film ispreferably arranged to be annular in shape, that is, arranged to becontinuous and provided at all circumferential positions, in the presentpreferred embodiment. Note, however, that the present invention is notlimited to the present preferred embodiment. For example, eachoil-repellent film 86 may be arranged at only some circumferentialpositions.

Referring to FIG. 29, the third outer circumferential surface 4223 maybe an annular surface extending perpendicularly or substantiallyperpendicularly to the central axis. Also, the third outercircumferential surface 4223 may be arranged to have a radial widthsmaller than the axial width of the second outer circumferential surface4222.

Also, referring to FIG. 30, the inner annular projecting portion 461 mayalternatively be arranged to project upward.

At least one of the first outer circumferential surface 4221 and theinner circumferential surface of the tubular portion 54 may include apumping groove array arranged to direct the lubricating oil 45 axiallydownward in a modification of the above-described preferred embodiment.Once the motor 12 a is driven and starts rotating, a pressure is appliedby the pumping groove array to the lubricating oil 45 arranged in theupper seal gap 661, and this pressure induces the lubricating oil 45 toflow downward. This contributes to preventing the lubricating oil 45from flowing upward out of the upper seal gap 661 and from beingscattered out of the upper seal gap 661. Note that both the pumpinggroove array and a tapered seal portion may be used in combination. Thismakes it possible to reduce the axial dimension of the tapered sealportion compared to a case where the surface of the lubricating oil 45is retained by only the tapered seal portion.

The second outer circumferential surface 4222 may include an annularrecessed portion. The recessed portion serves as a mark indicating aposition for the application of an oil-repellent agent, and makes iteasier to properly apply the oil-repellent agent onto a predeterminedposition.

The upper surface of the tubular portion 54 may include an annularminute recessed portion. More specifically, in this case, the minuterecessed portion is defined between the contact surface 541 and achamfer 661 c. Thus, the minute recessed portion serves as a markindicating a position for the application of the oil-repellent agent,and makes it easier to properly apply the oil-repellent agent onto apredetermined position.

Features of the above-described preferred embodiments and modificationsthereof may be combined as appropriate as long as no conflict arises.

Preferred embodiments of the present invention is specificallyapplicable to motors used to drive a disk, however, the presentinvention is also usable in other types of motors.

Only selected preferred embodiments have been chosen to illustrate thepresent invention. To those skilled in the art, however, it will beapparent from the foregoing disclosure that various changes andmodifications can be made herein without departing from the scope of thepresent invention as defined in the appended claims. Furthermore, theforegoing description of the preferred embodiments according to thepresent invention is provided for illustration only, and not forlimiting the invention as defined by the appended claims and theirequivalents.

What is claimed is:
 1. A motor comprising: a stationary portionincluding a stator; and a rotating portion including a rotor magnet, androtatably supported by the stationary portion through a lubricating oil;wherein the stationary portion includes: a shaft portion centered on acentral axis extending in a vertical direction; and an upper thrustportion arranged to extend radially outward from an upper portion of theshaft portion; the upper thrust portion includes: a tubular first outercircumferential surface arranged radially outside the upper thrustportion; and a tubular second outer circumferential surface arrangedabove the first outer circumferential surface; the rotating portionincludes: a sleeve portion arranged opposite to an outer circumferentialsurface of the shaft portion and a lower surface of the upper thrustportion; a tubular portion arranged to extend upward from an outer edgeportion of the sleeve portion, and arranged opposite to an outercircumferential surface of the upper thrust portion; and an annularcover portion arranged to extend radially inward from the tubularportion; the lower surface of the upper thrust portion and an uppersurface of the sleeve portion are arranged to together define an upperthrust gap therebetween, the lubricating oil is arranged in the upperthrust gap, the outer circumferential surface of the upper thrustportion and an inner circumferential surface of the tubular portion arearranged to together define an upper seal portion therebetween, theupper thrust gap is arranged to be in communication with the upper sealportion, and the upper seal portion includes a surface of thelubricating oil located therein; the annular cover portion includes: aplate portion arranged to extend radially; and an inner annularprojecting portion arranged radially inward of the plate portion, andarranged to project upward or downward; an inner circumferential surfaceof the inner annular projecting portion is arranged above the innercircumferential surface of the tubular portion; the innercircumferential surface of the inner annular projecting portion and thesecond outer circumferential surface are arranged opposite to each otherwith an axially extending gap intervening therebetween; and the gap isarranged to have a radial width smaller than a maximum width of theupper seal portion.
 2. The motor according to claim 1, wherein the firstouter circumferential surface is arranged radially outward of the secondouter circumferential surface.
 3. The motor according to claim 1,wherein the first outer circumferential surface includes an inclinedsurface arranged to obliquely extend radially inward and axially upwardsuch that a radial distance between the first outer circumferentialsurface and the inner circumferential surface of the tubular portionincreases with increasing height.
 4. The motor according to claim 1,wherein at least one of the first outer circumferential surface and theinner circumferential surface of the tubular portion includes a dynamicpressure generation portion arranged to induce an axially downwardpressure acting on the lubricating oil.
 5. The motor according to claim1, wherein the surface of the lubricating oil is located between thefirst outer circumferential surface and the inner circumferentialsurface of the tubular portion.
 6. The motor according to claim 1,wherein the upper thrust portion further includes an annular third outercircumferential surface arranged to join the first and second outercircumferential surfaces to each other.
 7. The motor according to claim6, wherein the third outer circumferential surface includes a flatannular surface arranged to extend perpendicularly or substantiallyperpendicularly to the central axis.
 8. The motor according to claim 6,wherein the upper thrust portion further includes an annular grooveportion recessed downward between the second and third outercircumferential surfaces.
 9. The motor according to claim 7, wherein thethird outer circumferential surface is arranged to have a radial widthsmaller than an axial width of the second outer circumferential surface.10. The motor according to claim 6, wherein the third outercircumferential surface is arranged to have a radial width smaller thanan axial width of the second outer circumferential surface, and includesan annular inclined surface arranged to extend radially outward andaxially downward.
 11. The motor according to claim 10, wherein the thirdouter circumferential surface is arranged to axially overlap with alower surface of the inner annular projecting portion.
 12. The motoraccording to claim 1, wherein an upper end of the second outercircumferential surface is arranged at an axial height higher than thatof an upper end of the inner annular projecting portion.
 13. The motoraccording to claim 1, wherein the inner annular projecting portion isarranged to project downward.
 14. The motor according to claim 1,wherein the annular cover portion includes an annular inclined portionarranged to obliquely extend radially outward and axially downward. 15.The motor according to claim 6, wherein a radial distance between aninner circumferential surface of the annular cover portion and thesecond outer circumferential surface is shorter than an axial distancebetween a lower surface of the annular cover portion and the third outercircumferential surface.
 16. The motor according to claim 1, wherein anupper surface of the tubular portion includes a first oil-repellent filmportion on which an oil-repellent film is arranged, the firstoil-repellent film portion being annular and arranged to surround thecentral axis.
 17. The motor according to claim 16, wherein the uppersurface of the tubular portion includes a contact surface arranged to bein axial contact with a lower surface of the annular cover portion; andat least a portion of the first oil-repellent film portion is arrangedradially inward of the contact surface.
 18. The motor according to claim6, wherein at least one of the second and third outer circumferentialsurfaces includes a second oil-repellent film portion on which at leasta portion of an oil-repellent film is arranged, the second oil-repellentfilm portion being annular and arranged to surround the central axis.19. The motor according to claim 1, wherein the inner circumferentialsurface of the inner annular projecting portion includes a thirdoil-repellent film portion on which an oil-repellent film is arranged,the third oil-repellent film portion being tubular and arranged tosurround the central axis.
 20. The motor according to claim 19, whereinthe second outer circumferential surface includes a second oil-repellentfilm portion on which at least a portion of an oil-repellent film isarranged; and the third oil-repellent film portion is arranged radiallyopposite to the second oil-repellent film portion.
 21. The motoraccording to claim 1, wherein the first outer circumferential surface isarranged radially outward of the second outer circumferential surface;the first outer circumferential surface includes an inclined surfacearranged to obliquely extend radially inward and axially upward suchthat a radial distance between the first outer circumferential surfaceand the inner circumferential surface of the tubular portion increaseswith increasing height; the upper thrust portion further includes anannular third outer circumferential surface arranged to join the firstand second outer circumferential surfaces to each other; the third outercircumferential surface is arranged to have a radial width smaller thanan axial width of the second outer circumferential surface, and includesan annular inclined surface arranged to extend radially outward andaxially downward; the third outer circumferential surface is arranged toaxially overlap with a lower surface of the inner annular projectingportion; an upper end of the second outer circumferential surface isarranged at an axial height higher than that of an upper end of theinner annular projecting portion; the annular projecting portion isarranged to project downward; the annular cover portion includes anannular inclined portion arranged to obliquely extend radially outwardand axially downward; a radial distance between an inner circumferentialsurface of the annular cover portion and the second outercircumferential surface is shorter than an axial distance between alower surface of the annular cover portion and the third outercircumferential surface; an upper surface of the tubular portionincludes a first oil-repellent film portion on which an oil-repellentfilm is arranged, the first oil-repellent film portion being annular andarranged to surround the central axis; the tubular portion includes acontact surface arranged to be in axial contact with the lower surfaceof the annular cover portion; at least a portion of the firstoil-repellent film portion is arranged radially inward of the contactsurface; at least one of the second and third outer circumferentialsurfaces includes a second oil-repellent film portion on which at leasta portion of an oil-repellent film is arranged, the second oil-repellentfilm portion being annular and arranged to surround the central axis; aninner circumferential surface of the inner annular projecting portionincludes a third oil-repellent film portion on which an oil-repellentfilm is arranged, the third oil-repellent film portion being tubular andarranged to surround the central axis; and the third oil-repellent filmportion is arranged axially opposite to the second oil-repellent filmportion.
 22. A storage disk drive comprising: the motor of claim 1arranged to rotate a disk; an access portion arranged to perform atleast one of reading and writing of information from or to the disk; anda housing arranged to contain the disk, the motor, and the accessportion.